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Common Sensing: Using satellite imagery to tackle climate change and natural disasters

Improved resilience to climate change. Disaster risk reduction. Better urban planning. Satellite imagery that shows land changes over time is helping achieve this in the Pacific.

Small island developing states in the Pacific (Fiji, Vanuatu, and the Solomon Islands) are at particular risk from climate change. The UK Space Agency funded ‘CommonSensing’ project is aiming to improve the islands’ resilience, using this satellite imagery in Data Cubes.

Most Data Cubes contain all the satellite imagery for an area back to the 1980s. By looking at this, it’s possible to see changes over time in terms of coastal erosion, coastal deposition, deforestation, urbanisation and landslide activity.

Richard explains ‘In the tropics there’s a lot of cloud cover which makes it harder to get a complete picture of how an area has changed over time. So search engines and machine learning are now being used to pick out the cloud-free bits of the satellite image. It then mosaics together all the cloud-free areas, from within a month or two either side of a given date. So you end up with, what appears to be, a cloud-free image. Google Earth Engine is a great example of this new technology’.

This is a type of Analysis Ready Data (ARD). And through machine learning the team are starting to process decades of satellite images, producing ARD maps for features such as coastal erosion, landslide activity, deforestation and urban growth. Those ARD maps will be easily accessible for policy makers, urban planners and decision makers.

Richard’s team is also advising on new satellite-derived data layers to put into the Data Cubes. They’ve highlighted a lack of nationwide elevation data in many low-income countries. This enables users to predict where the steep slopes are, and where the flow of the water and flooding is going to be. Another useful set of data is coastal water depth, which can be used to highlight areas susceptible to tsunami or storm surge flooding. If there is a very gentle coastal gradient, there is a much more severe run-up effect.

After a major storm there is redevelopment, often with things rebuilt in the same place as before. Often those buildings then get destroyed by the next storm. The Data Cubes show where hazardous locations are, such as zones of flooding, erosion or landslides. This information allows better long-term planning and development, such as where key facilities should be located to withstand storms.

The project is raising awareness of the free resources available from satellite technologies. And is educating government technical officers, community leaders and NGOs on how use this data to inform decision making. Making communities safer and more resilient in the long run.

Caribbean Hurricane Resilience

Satellite technologies are also being used in Dominica, and neighbouring Caribbean islands, to improve resilience to hurricanes, with their associated landslides and flooding.

In 2017 Hurricane Maria – one of the largest storms ever to hit the Caribbean – devastated Dominica. Just after, Richard and his colleagues surveyed the damage. Using satellite imagery, Richard and his colleagues can see what changed after this disastrous event.

‘We’re looking at how communities can cope better with the impacts of the hazards they face. So that involves highlighting hazardous areas, such as where you are likely get landslides and debris flows in a hurricane, so they can be avoided when rebuilding.’

And from that, they’re advising the government on how to ‘build back better’. For example, which bridges survived and why did they survive? This forms the basis of recommendations to the government of Dominica on building bridges designed to cope with debris flows ‘armed’ with large boulders and tree trunks.

We are living in a golden age of freely available, detailed satellite imagery, which can help reduce the risk of disasters. Richard is determined to use this to the best advantage of the people who need it most.